1. Field of the Invention
The present invention relates generally to image processing in a printing apparatus and particularly to image processing for automatically carrying out many complicated settings required for realizing a visual effect selection in printing-out using a color toner and a particular toner.
2. Description of the Related Art
Recently, a digital printing technology has surely increased its utility value in the on-demand printing market and the document printing market for small number of volumes. Particularly full color printing using an electrophotographic technology is rapidly obtaining a bigger market because of the advantage thereof over the other printing technology in an aspect such as productivity, printing cost and maintainability. Among the technologies, particularly in addition to the full color printing by the conventional electrophotographic printing using basic four color tonners of CMYBk, a multi-color printing method further using a particular toner is getting attention and obtaining a bigger share in a particular printing market which requires a high on-demand capability and real-time capability. The particular tonner includes, for example, a transparent toner which can absorb irregularity on the surface of printed material to achieve a high gloss, and a light toner which can suppress roughness in a highlighted part. By using the particular toner, it becomes possible to obtain a new added value different from that of the typical digital printing and further widen the digital printing world. On such a background, a color composite machine (hereinafter, MFP) mounting a particular toner is being introduced into the market.
The MFP retains image data and attribute information corresponding to each pixel of the image data in a memory, performs image processing on the image data according to the attribute information, and carries out printing. For mounting the particular toner, the MFP develops print data of the particular toner into a binary drawing pattern and combines the data with the attribute information. The MFP performs the image processing on the image data such as color conversion and screen processing according to the attribute information, generates a drawing pattern of the basic four color toners of CMYBk, and takes out the particular toner drawing pattern combined with the attribute information. Then, the MFP sends the basic four color drawing pattern and the particular toner drawing pattern to a print engine for carrying out printing.
The memory for retaining the image data and the attribute information has predetermined storage capacity limit for each of the image data and the attribute information. Accordingly, the image data is compressed for retention by lossy compression so as to have a data amount smaller than the predetermined storage capacity. Meanwhile, the attribute information is compressed by lossless compression to prevent bit loss and sometimes the attribute information amount exceeds the predetermined capacity. For processing the case of exceeding the predetermined capacity, Japanese Patent Laid-Open No. 2006-086649 proposes a technique which increases a compression rate by masking (replacing by a specific value) each bit of the attribute information and thereby reduces the attribute information amount to that smaller than the predetermined capacity for storing.
However, in the technique of the above patent publication, since the particular toner drawing pattern is combined with the attribute information for retention, there is a problem that the particular toner drawing pattern information is erased and the particular toner printing cannot be carried out when each bit of the attribute information is masked.